Chapter 4 ________________________________________________________________ Operation 
VAISALA_______________________________________________________________________ 55 
Chemical purge
Calibration
values
Measured values
after chemical
exposure
Humidit
Output signal
 
 0507-056 
Figure 16  Decrease of Sensor Gain Due to Interfering Chemical 
and Effect of Chemical Purge Process 
Automatic/Manual Chemical Purge 
When HMT310 leaves the factory the automatic chemical purge (if 
selected) takes place repeatedly with the time intervals set in the factory. 
You can change the interval in which the purge takes place by using 
serial commands. This may be necessary if the measuring environment 
contains high concentrations of interfering chemicals. The automatic 
chemical purge can be also turned off if necessary. 
Automatic Chemical Purge Settings 
PUR Turn ON/OFF Automatic Chemical 
Purge  
This command enables or disables automatic chemical purge.  
Syntax: PUR x<cr> 
Where 
x = ON/OFF